package com.msoft.common.util;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.ByteBuffer;

import org.apache.log4j.Logger;

/**
 * Utility class that handles byte arrays, conversions to/from other types,
 * comparisons, hash code generation, manufacturing keys for HashMaps or
 * HashSets, etc.
 */
public class BytesUtils {
	
	private static final Logger logger = Logger.getLogger(BytesUtils.class);

	public static final String UTF8_ENCODING = "UTF-8";
	/**
	 * Size of boolean in bytes
	 */
	public static final int SIZEOF_BOOLEAN = Byte.SIZE / Byte.SIZE;

	/**
	 * Size of byte in bytes
	 */
	public static final int SIZEOF_BYTE = SIZEOF_BOOLEAN;

	/**
	 * Size of char in bytes
	 */
	public static final int SIZEOF_CHAR = Character.SIZE / Byte.SIZE;

	/**
	 * Size of double in bytes
	 */
	public static final int SIZEOF_DOUBLE = Double.SIZE / Byte.SIZE;

	/**
	 * Size of float in bytes
	 */
	public static final int SIZEOF_FLOAT = Float.SIZE / Byte.SIZE;

	/**
	 * Size of int in bytes
	 */
	public static final int SIZEOF_INT = Integer.SIZE / Byte.SIZE;

	/**
	 * Size of long in bytes
	 */
	public static final int SIZEOF_LONG = Long.SIZE / Byte.SIZE;

	/**
	 * Size of short in bytes
	 */
	public static final int SIZEOF_SHORT = Short.SIZE / Byte.SIZE;

	/**
	 * Estimate of size cost to pay beyond payload in jvm for instance of byte
	 * []. Estimate based on study of jhat and jprofiler numbers.
	 */
	// JHat says BU is 56 bytes.
	// SizeOf which uses java.lang.instrument says 24 bytes. (3 longs?)
	public static final int ESTIMATED_HEAP_TAX = 16;

	public static Object fromBytes(Class<?> cls, byte[] buff) {
		if (String.class.getName().equals(cls.getName())) {
			return toString(buff);
		} else if (Integer.class.getName().equals(cls.getName())) {
			return toInt(buff);
		} else if (Character.class.getName().equals(cls.getName())) {
			return (char) buff[0];
		} else if (byte[].class.getName().equals(cls.getName())) {
			return buff;

		}
		return null;
	}

	public static byte[] toBytesEx(Object obj, int len) {

		if (String.class.getName().equals(obj.getClass().getName())) {
			return toBytes((String) obj, len);
		} else if (Integer.class.getName().equals(obj.getClass().getName())) {
			return toBytes((Integer) obj);
		} else if (Byte.class.getName().equals(obj.getClass().getName())) {
			byte[] tmp = new byte[1];
			tmp[0] = (Byte) obj;
			return tmp;
		} else if (byte[].class.getName().equals(obj.getClass().getName())) {
			return (byte[]) obj;

		}
		return null;
	}

	/**
	 * Put bytes at the specified byte array position.
	 * 
	 * @param tgtBytes
	 *            the byte array
	 * @param tgtOffset
	 *            position in the array
	 * @param srcBytes
	 *            array to write out
	 * @param srcOffset
	 *            source offset
	 * @param srcLength
	 *            source length
	 * @return incremented offset
	 */
	public static int putBytes(byte[] tgtBytes, int tgtOffset, byte[] srcBytes,
			int srcOffset, int srcLength) {
		System.arraycopy(srcBytes, srcOffset, tgtBytes, tgtOffset, srcLength);
		return tgtOffset + srcLength;
	}

	/**
	 * Write a single byte out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param b
	 *            byte to write out
	 * @return incremented offset
	 */
	public static int putByte(byte[] bytes, int offset, byte b) {
		bytes[offset] = b;
		return offset + 1;
	}

	/**
	 * Returns a new byte array, copied from the passed ByteBuffer.
	 * 
	 * @param bb
	 *            A ByteBuffer
	 * @return the byte array
	 */
	public static byte[] toBytes(ByteBuffer bb) {
		int length = bb.limit();
		byte[] result = new byte[length];
		System.arraycopy(bb.array(), bb.arrayOffset(), result, 0, length);
		return result;
	}

	/**
	 * @param b
	 *            Presumed UTF-8 encoded byte array.
	 * @return String made from <code>b</code>
	 */
	public static String toString(final byte[] b) {
		if (b == null) {
			return null;
		}
		return toString(b, 0, b.length);
	}

	/**
	 * Joins two byte arrays together using a separator.
	 * 
	 * @param b1
	 *            The first byte array.
	 * @param sep
	 *            The separator to use.
	 * @param b2
	 *            The second byte array.
	 */
	public static String toString(final byte[] b1, String sep, final byte[] b2) {
		return toString(b1, 0, b1.length) + sep + toString(b2, 0, b2.length);
	}

	/**
	 * This method will convert utf8 encoded bytes into a string. If an
	 * UnsupportedEncodingException occurs, this method will eat it and return
	 * null instead.
	 * 
	 * @param b
	 *            Presumed UTF-8 encoded byte array.
	 * @param off
	 *            offset into array
	 * @param len
	 *            length of utf-8 sequence
	 * @return String made from <code>b</code> or null
	 */
	public static String toString(final byte[] b, int off, int len) {
		if (b == null) {
			return null;
		}
		if (len == 0) {
			return "";
		}
		try {
			return new String(b, off, len, UTF8_ENCODING);
		} catch (UnsupportedEncodingException e) {
			// LOG.error("UTF-8 not supported?", e);
			return null;
		}
	}

	public static String toString(final byte[] b, int off, int len, boolean trim) {
		if (b == null) {
			return null;
		}
		if (len == 0) {
			return "";
		}
		try {
			if (trim) {
				return new String(b, off, len, UTF8_ENCODING).trim();
			} else {
				return new String(b, off, len, UTF8_ENCODING);
			}

		} catch (UnsupportedEncodingException e) {
			// LOG.error("UTF-8 not supported?", e);
			return null;
		}
	}

	/**
	 * Write a printable representation of a byte array.
	 * 
	 * @param b
	 *            byte array
	 * @return string
	 * @see #toStringBinary(byte[], int, int)
	 */
	public static String toStringBinary(final byte[] b) {
		if (b == null)
			return "null";
		return toStringBinary(b, 0, b.length);
	}

	/**
	 * Converts the given byte buffer, from its array offset to its limit, to a
	 * string. The position and the mark are ignored.
	 * 
	 * @param buf
	 *            a byte buffer
	 * @return a string representation of the buffer's binary contents
	 */
	public static String toStringBinary(ByteBuffer buf) {
		if (buf == null)
			return "null";
		return toStringBinary(buf.array(), buf.arrayOffset(), buf.limit());
	}

	/**
	 * Write a printable representation of a byte array. Non-printable
	 * characters are hex escaped in the format \\x%02X, eg: \x00 \x05 etc
	 * 
	 * @param b
	 *            array to write out
	 * @param off
	 *            offset to start at
	 * @param len
	 *            length to write
	 * @return string output
	 */
	public static String toStringBinary(final byte[] b, int off, int len) {
		StringBuilder result = new StringBuilder();
		try {
			String first = new String(b, off, len, "ISO-8859-1");
			for (int i = 0; i < first.length(); ++i) {
				int ch = first.charAt(i) & 0xFF;
				if ((ch >= '0' && ch <= '9')
						|| (ch >= 'A' && ch <= 'Z')
						|| (ch >= 'a' && ch <= 'z')
						|| " `~!@#$%^&*()-_=+[]{}\\|;:'\",.<>/?".indexOf(ch) >= 0) {
					result.append(first.charAt(i));
				} else {
					result.append(String.format("\\x%02X", ch));
				}
			}
		} catch (UnsupportedEncodingException e) {
			// LOG.error("ISO-8859-1 not supported?", e);
		}
		return result.toString();
	}

	private static boolean isHexDigit(char c) {
		return (c >= 'A' && c <= 'F') || (c >= '0' && c <= '9');
	}

	/**
	 * Takes a ASCII digit in the range A-F0-9 and returns the corresponding
	 * integer/ordinal value.
	 * 
	 * @param ch
	 *            The hex digit.
	 * @return The converted hex value as a byte.
	 */
	public static byte toBinaryFromHex(byte ch) {
		if (ch >= 'A' && ch <= 'F')
			return (byte) ((byte) 10 + (byte) (ch - 'A'));
		// else
		return (byte) (ch - '0');
	}

	public static byte[] toBytesBinary(String in) {
		// this may be bigger than we need, but let's be safe.
		byte[] b = new byte[in.length()];
		int size = 0;
		for (int i = 0; i < in.length(); ++i) {
			char ch = in.charAt(i);
			if (ch == '\\' && in.length() > i + 1 && in.charAt(i + 1) == 'x') {
				// ok, take next 2 hex digits.
				char hd1 = in.charAt(i + 2);
				char hd2 = in.charAt(i + 3);

				// they need to be A-F0-9:
				if (!isHexDigit(hd1) || !isHexDigit(hd2)) {
					// bogus escape code, ignore:
					continue;
				}
				// turn hex ASCII digit -> number
				byte d = (byte) ((toBinaryFromHex((byte) hd1) << 4) + toBinaryFromHex((byte) hd2));

				b[size++] = d;
				i += 3; // skip 3
			} else {
				b[size++] = (byte) ch;
			}
		}
		// resize:
		byte[] b2 = new byte[size];
		System.arraycopy(b, 0, b2, 0, size);
		return b2;
	}

	/**
	 * Converts a string to a UTF-8 byte array.
	 * 
	 * @param s
	 *            string
	 * @return the byte array
	 */
	public static byte[] toBytes(String s) {
		try {
			return s.getBytes(UTF8_ENCODING);
		} catch (UnsupportedEncodingException e) {
			// LOG.error("UTF-8 not supported?", e);
			return null;
		}
	}

	/**
	 * Converts a string to a UTF-8 byte array.
	 * 
	 * @param s
	 *            string
	 * @return the byte array
	 */
	public static byte[] toBytes(String s, int len) {
		try {
			byte[] tmp = new byte[len];
			byte[] src = s.getBytes(UTF8_ENCODING);
			if (len > src.length) {
				len = src.length;
			}
			System.arraycopy(s.getBytes(UTF8_ENCODING), 0, tmp, 0, len);
			return tmp;
		} catch (UnsupportedEncodingException e) {
			// LOG.error("UTF-8 not supported?", e);
			return null;
		}
	}

	/**
	 * Convert a boolean to a byte array. True becomes -1 and false becomes 0.
	 * 
	 * @param b
	 *            value
	 * @return <code>b</code> encoded in a byte array.
	 */
	public static byte[] toBytes(final boolean b) {
		return new byte[] { b ? (byte) -1 : (byte) 0 };
	}

	/**
	 * Reverses {@link #toBytes(boolean)}
	 * 
	 * @param b
	 *            array
	 * @return True or false.
	 */
	public static boolean toBoolean(final byte[] b) {
		if (b.length != 1) {
			throw new IllegalArgumentException("Array has wrong size: "
					+ b.length);
		}
		return b[0] != (byte) 0;
	}

	/**
	 * Convert a long value to a byte array using big-endian.
	 * 
	 * @param val
	 *            value to convert
	 * @return the byte array
	 */
	public static byte[] toBytes(long val) {
		byte[] b = new byte[8];
		for (int i = 7; i > 0; i--) {
			b[i] = (byte) val;
			val >>>= 8;
		}
		b[0] = (byte) val;
		return b;
	}

	/**
	 * Converts a byte array to a long value. Reverses {@link #toBytes(long)}
	 * 
	 * @param bytes
	 *            array
	 * @return the long value
	 */
	public static long toLong(byte[] bytes) {
		return toLong(bytes, 0, SIZEOF_LONG);
	}

	/**
	 * Converts a byte array to a long value. Assumes there will be
	 * {@link #SIZEOF_LONG} bytes available.
	 * 
	 * @param bytes
	 *            bytes
	 * @param offset
	 *            offset
	 * @return the long value
	 */
	public static long toLong(byte[] bytes, int offset) {
		return toLong(bytes, offset, SIZEOF_LONG);
	}

	/**
	 * Converts a byte array to a long value.
	 * 
	 * @param bytes
	 *            array of bytes
	 * @param offset
	 *            offset into array
	 * @param length
	 *            length of data (must be {@link #SIZEOF_LONG})
	 * @return the long value
	 * @throws IllegalArgumentException
	 *             if length is not {@link #SIZEOF_LONG} or if there's not
	 *             enough room in the array at the offset indicated.
	 */
	public static long toLong(byte[] bytes, int offset, final int length) {
		if (length != SIZEOF_LONG || offset + length > bytes.length) {
			throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_LONG);
		}
		long l = 0;
		for (int i = offset; i < offset + length; i++) {
			l <<= 8;
			l ^= bytes[i] & 0xFF;
		}
		return l;
	}

	private static IllegalArgumentException explainWrongLengthOrOffset(
			final byte[] bytes, final int offset, final int length,
			final int expectedLength) {
		String reason;
		if (length != expectedLength) {
			reason = "Wrong length: " + length + ", expected " + expectedLength;
		} else {
			reason = "offset (" + offset + ") + length (" + length
					+ ") exceed the" + " capacity of the array: "
					+ bytes.length;
		}
		return new IllegalArgumentException(reason);
	}

	/**
	 * Put a long value out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param val
	 *            long to write out
	 * @return incremented offset
	 * @throws IllegalArgumentException
	 *             if the byte array given doesn't have enough room at the
	 *             offset specified.
	 */
	public static int putLong(byte[] bytes, int offset, long val) {
		if (bytes.length - offset < SIZEOF_LONG) {
			throw new IllegalArgumentException(
					"Not enough room to put a long at" + " offset " + offset
							+ " in a " + bytes.length + " byte array");
		}
		for (int i = offset + 7; i > offset; i--) {
			bytes[i] = (byte) val;
			val >>>= 8;
		}
		bytes[offset] = (byte) val;
		return offset + SIZEOF_LONG;
	}

	/**
	 * Presumes float encoded as IEEE 754 floating-point "single format"
	 * 
	 * @param bytes
	 *            byte array
	 * @return Float made from passed byte array.
	 */
	public static float toFloat(byte[] bytes) {
		return toFloat(bytes, 0);
	}

	/**
	 * Presumes float encoded as IEEE 754 floating-point "single format"
	 * 
	 * @param bytes
	 *            array to convert
	 * @param offset
	 *            offset into array
	 * @return Float made from passed byte array.
	 */
	public static float toFloat(byte[] bytes, int offset) {
		return Float.intBitsToFloat(toInt(bytes, offset, SIZEOF_INT));
	}

	/**
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset to write to
	 * @param f
	 *            float value
	 * @return New offset in <code>bytes</code>
	 */
	public static int putFloat(byte[] bytes, int offset, float f) {
		return putInt(bytes, offset, Float.floatToRawIntBits(f));
	}

	/**
	 * @param f
	 *            float value
	 * @return the float represented as byte []
	 */
	public static byte[] toBytes(final float f) {
		// Encode it as int
		return BytesUtils.toBytes(Float.floatToRawIntBits(f));
	}

	/**
	 * @param bytes
	 *            byte array
	 * @return Return double made from passed bytes.
	 */
	public static double toDouble(final byte[] bytes) {
		return toDouble(bytes, 0);
	}

	/**
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset where double is
	 * @return Return double made from passed bytes.
	 */
	public static double toDouble(final byte[] bytes, final int offset) {
		return Double.longBitsToDouble(toLong(bytes, offset, SIZEOF_LONG));
	}

	/**
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset to write to
	 * @param d
	 *            value
	 * @return New offset into array <code>bytes</code>
	 */
	public static int putDouble(byte[] bytes, int offset, double d) {
		return putLong(bytes, offset, Double.doubleToLongBits(d));
	}

	/**
	 * Serialize a double as the IEEE 754 double format output. The resultant
	 * array will be 8 bytes long.
	 * 
	 * @param d
	 *            value
	 * @return the double represented as byte []
	 */
	public static byte[] toBytes(final double d) {
		// Encode it as a long
		return BytesUtils.toBytes(Double.doubleToRawLongBits(d));
	}

	/**
	 * Convert an int value to a byte array
	 * 
	 * @param val
	 *            value
	 * @return the byte array
	 */
	public static byte[] toBytes(int val) {
		byte[] b = new byte[4];
		for (int i = 3; i > 0; i--) {
			b[i] = (byte) val;
			val >>>= 8;
		}
		b[0] = (byte) val;
		return b;
	}

	/**
	 * Converts a byte array to an int value
	 * 
	 * @param bytes
	 *            byte array
	 * @return the int value
	 */
	public static int toInt(byte[] bytes) {
		return toInt(bytes, 0, SIZEOF_INT);
	}

	/**
	 * Converts a byte array to an int value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @return the int value
	 */
	public static int toInt(byte[] bytes, int offset) {
		return toInt(bytes, offset, SIZEOF_INT);
	}

	/**
	 * Converts a byte array to an int value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @param length
	 *            length of int (has to be {@link #SIZEOF_INT})
	 * @return the int value
	 * @throws IllegalArgumentException
	 *             if length is not {@link #SIZEOF_INT} or if there's not enough
	 *             room in the array at the offset indicated.
	 */
	public static int toInt(byte[] bytes, int offset, final int length) {
		if (length != SIZEOF_INT || offset + length > bytes.length) {
			throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_INT);
		}
		int n = 0;
		for (int i = offset; i < (offset + length); i++) {
			n <<= 8;
			n ^= bytes[i] & 0xFF;
		}
		return n;
	}

	/**
	 * Put an int value out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param val
	 *            int to write out
	 * @return incremented offset
	 * @throws IllegalArgumentException
	 *             if the byte array given doesn't have enough room at the
	 *             offset specified.
	 */
	public static int putInt(byte[] bytes, int offset, int val) {
		if (bytes.length - offset < SIZEOF_INT) {
			throw new IllegalArgumentException(
					"Not enough room to put an int at" + " offset " + offset
							+ " in a " + bytes.length + " byte array");
		}
		for (int i = offset + 3; i > offset; i--) {
			bytes[i] = (byte) val;
			val >>>= 8;
		}
		bytes[offset] = (byte) val;
		return offset + SIZEOF_INT;
	}

	/**
	 * Convert a short value to a byte array of {@link #SIZEOF_SHORT} bytes
	 * long.
	 * 
	 * @param val
	 *            value
	 * @return the byte array
	 */
	public static byte[] toBytes(short val) {
		byte[] b = new byte[SIZEOF_SHORT];
		b[1] = (byte) val;
		val >>= 8;
		b[0] = (byte) val;
		return b;
	}

	/**
	 * Converts a byte array to a short value
	 * 
	 * @param bytes
	 *            byte array
	 * @return the short value
	 */
	public static short toShort(byte[] bytes) {
		return toShort(bytes, 0, SIZEOF_SHORT);
	}

	/**
	 * Converts a byte array to a short value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @return the short value
	 */
	public static short toShort(byte[] bytes, int offset) {
		return toShort(bytes, offset, SIZEOF_SHORT);
	}

	/**
	 * Converts a byte array to a short value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @param length
	 *            length, has to be {@link #SIZEOF_SHORT}
	 * @return the short value
	 * @throws IllegalArgumentException
	 *             if length is not {@link #SIZEOF_SHORT} or if there's not
	 *             enough room in the array at the offset indicated.
	 */
	public static short toShort(byte[] bytes, int offset, final int length) {
		if (length != SIZEOF_SHORT || offset + length > bytes.length) {
			throw explainWrongLengthOrOffset(bytes, offset, length,
					SIZEOF_SHORT);
		}
		short n = 0;
		n ^= bytes[offset] & 0xFF;
		n <<= 8;
		n ^= bytes[offset + 1] & 0xFF;
		return n;
	}

	/**
	 * This method will get a sequence of bytes from pos -> limit, but will
	 * restore pos after.
	 * 
	 * @param buf
	 * @return byte array
	 */
	public static byte[] getBytes(ByteBuffer buf) {
		int savedPos = buf.position();
		byte[] newBytes = new byte[buf.remaining()];
		buf.get(newBytes);
		buf.position(savedPos);
		return newBytes;
	}

	/**
	 * Put a short value out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param val
	 *            short to write out
	 * @return incremented offset
	 * @throws IllegalArgumentException
	 *             if the byte array given doesn't have enough room at the
	 *             offset specified.
	 */
	public static int putShort(byte[] bytes, int offset, short val) {
		if (bytes.length - offset < SIZEOF_SHORT) {
			throw new IllegalArgumentException(
					"Not enough room to put a short at" + " offset " + offset
							+ " in a " + bytes.length + " byte array");
		}
		bytes[offset + 1] = (byte) val;
		val >>= 8;
		bytes[offset] = (byte) val;
		return offset + SIZEOF_SHORT;
	}

	/**
	 * Convert a BigDecimal value to a byte array
	 * 
	 * @param val
	 * @return the byte array
	 */
	public static byte[] toBytes(BigDecimal val) {
		byte[] valueBytes = val.unscaledValue().toByteArray();
		byte[] result = new byte[valueBytes.length + SIZEOF_INT];
		int offset = putInt(result, 0, val.scale());
		putBytes(result, offset, valueBytes, 0, valueBytes.length);
		return result;
	}

	/**
	 * Converts a byte array to a BigDecimal
	 * 
	 * @param bytes
	 * @return the char value
	 */
	public static BigDecimal toBigDecimal(byte[] bytes) {
		return toBigDecimal(bytes, 0, bytes.length);
	}

	/**
	 * Converts a byte array to a BigDecimal value
	 * 
	 * @param bytes
	 * @param offset
	 * @param length
	 * @return the char value
	 */
	public static BigDecimal toBigDecimal(byte[] bytes, int offset,
			final int length) {
		if (bytes == null || length < SIZEOF_INT + 1
				|| (offset + length > bytes.length)) {
			return null;
		}

		int scale = toInt(bytes, offset);
		byte[] tcBytes = new byte[length - SIZEOF_INT];
		System.arraycopy(bytes, offset + SIZEOF_INT, tcBytes, 0, length
				- SIZEOF_INT);
		return new BigDecimal(new BigInteger(tcBytes), scale);
	}

	/**
	 * Put a BigDecimal value out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param val
	 *            BigDecimal to write out
	 * @return incremented offset
	 */
	public static int putBigDecimal(byte[] bytes, int offset, BigDecimal val) {
		if (bytes == null) {
			return offset;
		}

		byte[] valueBytes = val.unscaledValue().toByteArray();
		byte[] result = new byte[valueBytes.length + SIZEOF_INT];
		offset = putInt(result, offset, val.scale());
		return putBytes(result, offset, valueBytes, 0, valueBytes.length);
	}

	/**
	 * @param a
	 *            first third
	 * @param b
	 *            second third
	 * @param c
	 *            third third
	 * @return New array made from a, b and c
	 */
	public static byte[] add(final byte[] a, final byte[] b, final byte[] c) {
		byte[] result = new byte[a.length + b.length + c.length];
		System.arraycopy(a, 0, result, 0, a.length);
		System.arraycopy(b, 0, result, a.length, b.length);
		System.arraycopy(c, 0, result, a.length + b.length, c.length);
		return result;
	}

	/**
	 * @param a
	 *            array
	 * @param length
	 *            amount of bytes to grab
	 * @return First <code>length</code> bytes from <code>a</code>
	 */
	public static byte[] head(final byte[] a, final int length) {
		if (a.length < length) {
			return null;
		}
		byte[] result = new byte[length];
		System.arraycopy(a, 0, result, 0, length);
		return result;
	}

	/**
	 * @param a
	 *            array
	 * @param length
	 *            amount of bytes to snarf
	 * @return Last <code>length</code> bytes from <code>a</code>
	 */
	public static byte[] tail(final byte[] a, final int length) {
		if (a.length < length) {
			return null;
		}
		byte[] result = new byte[length];
		System.arraycopy(a, a.length - length, result, 0, length);
		return result;
	}

	/**
	 * @param bytes
	 *            array to hash
	 * @param offset
	 *            offset to start from
	 * @param length
	 *            length to hash
	 * */
	public static int hashCode(byte[] bytes, int offset, int length) {
		int hash = 1;
		for (int i = offset; i < offset + length; i++)
			hash = (31 * hash) + (int) bytes[i];
		return hash;
	}

	/**
	 * @param t
	 *            operands
	 * @return Array of byte arrays made from passed array of Text
	 */
	public static byte[][] toByteArrays(final String[] t) {
		byte[][] result = new byte[t.length][];
		for (int i = 0; i < t.length; i++) {
			result[i] = BytesUtils.toBytes(t[i]);
		}
		return result;
	}

	/**
	 * @param column
	 *            operand
	 * @return A byte array of a byte array where first and only entry is
	 *         <code>column</code>
	 */
	public static byte[][] toByteArrays(final String column) {
		return toByteArrays(toBytes(column));
	}

	/**
	 * @param column
	 *            operand
	 * @return A byte array of a byte array where first and only entry is
	 *         <code>column</code>
	 */
	public static byte[][] toByteArrays(final byte[] column) {
		byte[][] result = new byte[1][];
		result[0] = column;
		return result;
	}

	/**
	 * Binary search for keys in indexes.
	 * 
	 * @param arr
	 *            array of byte arrays to search for
	 * @param key
	 *            the key you want to find
	 * @param offset
	 *            the offset in the key you want to find
	 * @param length
	 *            the length of the key
	 * @param comparator
	 *            a comparator to compare.
	 * @return zero-based index of the key, if the key is present in the array.
	 *         Otherwise, a value -(i + 1) such that the key is between arr[i -
	 *         1] and arr[i] non-inclusively, where i is in [0, i], if we define
	 *         arr[-1] = -Inf and arr[N] = Inf for an N-element array. The above
	 *         means that this function can return 2N + 1 different values
	 *         ranging from -(N + 1) to N - 1.
	 */

	/**
	 * Bytewise binary increment/deincrement of long contained in byte array on
	 * given amount.
	 * 
	 * @param value
	 *            - array of bytes containing long (length <= SIZEOF_LONG)
	 * @param amount
	 *            value will be incremented on (deincremented if negative)
	 * @return array of bytes containing incremented long (length ==
	 *         SIZEOF_LONG)
	 */
	public static byte[] incrementBytes(byte[] value, long amount) {
		byte[] val = value;
		if (val.length < SIZEOF_LONG) {
			// Hopefully this doesn't happen too often.
			byte[] newvalue;
			if (val[0] < 0) {
				newvalue = new byte[] { -1, -1, -1, -1, -1, -1, -1, -1 };
			} else {
				newvalue = new byte[SIZEOF_LONG];
			}
			System.arraycopy(val, 0, newvalue, newvalue.length - val.length,
					val.length);
			val = newvalue;
		} else if (val.length > SIZEOF_LONG) {
			throw new IllegalArgumentException(
					"Increment Bytes - value too big: " + val.length);
		}
		if (amount == 0)
			return val;
		if (val[0] < 0) {
			return binaryIncrementNeg(val, amount);
		}
		return binaryIncrementPos(val, amount);
	}

	/* increment/deincrement for positive value */
	private static byte[] binaryIncrementPos(byte[] value, long amount) {
		long amo = amount;
		int sign = 1;
		if (amount < 0) {
			amo = -amount;
			sign = -1;
		}
		for (int i = 0; i < value.length; i++) {
			int cur = ((int) amo % 256) * sign;
			amo = (amo >> 8);
			int val = value[value.length - i - 1] & 0x0ff;
			int total = val + cur;
			if (total > 255) {
				amo += sign;
				total %= 256;
			} else if (total < 0) {
				amo -= sign;
			}
			value[value.length - i - 1] = (byte) total;
			if (amo == 0)
				return value;
		}
		return value;
	}

	/* increment/deincrement for negative value */
	private static byte[] binaryIncrementNeg(byte[] value, long amount) {
		long amo = amount;
		int sign = 1;
		if (amount < 0) {
			amo = -amount;
			sign = -1;
		}
		for (int i = 0; i < value.length; i++) {
			int cur = ((int) amo % 256) * sign;
			amo = (amo >> 8);
			int val = ((~value[value.length - i - 1]) & 0x0ff) + 1;
			int total = cur - val;
			if (total >= 0) {
				amo += sign;
			} else if (total < -256) {
				amo -= sign;
				total %= 256;
			}
			value[value.length - i - 1] = (byte) total;
			if (amo == 0)
				return value;
		}
		return value;
	}

	/**
	 * Writes a string as a fixed-size field, padded with zeros.
	 */
	public static void writeStringFixedSize(final DataOutput out, String s,
			int size) throws IOException {
		byte[] b = toBytes(s);
		if (b.length > size) {
			throw new IOException("Trying to write " + b.length + " bytes ("
					+ toStringBinary(b) + ") into a field of length " + size);
		}

		out.writeBytes(s);
		for (int i = 0; i < size - s.length(); ++i)
			out.writeByte(0);
	}

	/**
	 * Reads a fixed-size field and interprets it as a string padded with zeros.
	 */
	public static String readStringFixedSize(final DataInput in, int size)
			throws IOException {
		byte[] b = new byte[size];
		in.readFully(b);
		int n = b.length;
		while (n > 0 && b[n - 1] == 0)
			--n;

		return toString(b, 0, n);
	}

}
